1. Technical Field
The present invention relates to a printing apparatus provided with transmission cables for transmitting voltage signals to a liquid ejection head, and to the transmission cables.
2. Related Art
Among printers, each being an example of a printing apparatus, there is a printer including a liquid ejection head, a voltage signal generation circuit, and transmission cables and configured such that voltage signals generated by the voltage signal generation circuit are transmitted to the liquid ejection head using the transmission cables, and then are supplied to a plurality of piezoelectric elements included in the liquid ejection head to allow the liquid ejection head to eject liquids so as to allow characters and/or images to be printed on paper or any other printing medium.
In such a printer, it is important that the voltage signals, which are transmitted to the liquid ejection head using the transmission cables, are supplied to the piezoelectric elements without being distorted in the transmission cables. This is because, with the distortions of the transmitted voltage signals, the piezoelectric elements are not properly deformed (contracted and/or elongated), thereby causing the amount of liquid ejected by the deformation of each of the piezoelectric elements to be varied, and as a result, a situation in which correct sizes of dots are not formed on the paper and this formation of incorrect sizes of dots degrades the printing quality may occur. For this reason, there is a printer (a liquid ejection apparatus) in which, in order to realize the transmission of voltage signals (drive signals) whose distortions are reduced, in flexible flat cables (FFC), each being conventionally used as a transmission cable, each of conductors (signal lines) supplied with the respective voltage signals and each of conductors supplied with a constant voltage (a ground signal) are respectively branched into branched voltage-signal conductors and branched constant-voltage conductors, and the branched voltage-signal conductors and the branched constant-voltage conductors are allocated such that the branched voltage-signal conductors and the branched constant-voltage conductors are adjacent to each other (for example, JP-A-2003-226006). Further, there is a printer (a liquid ejection apparatus) in which, in order to realize the transmission of voltage signals (drive signals) the distortions of which are reduced and which are unlikely to be influenced by external disturbances (for example, an electromagnetic wave applied from the outside), coaxial cables are employed, as the transmission cables, in substitution for the flexible flat cables (FFC) (for example, JP-A-2012-206284).
By the way, in a printer configured to allow a carriage that reciprocates to include a liquid ejection head, when the movement distance of the carriage when the carriage reciprocates is increased because of the large width of printing paper or any other reason, the length of each of the transmission cables becomes large in accordance with the increase of the movement distance of the carriage. Thus, in the transmission cables whose lengths have become large, the values of inductance elements and resistance elements of the conductors increase, and as a result, a situation in which distortions are more likely to arise in the voltage signals transmitted in the transmission cables occurs.
In such a situation, since the printer disclosed in JP-A-2003-226006 allows each of the conductors included in the flexible flat cables to be branched into branched conductors so as to reduce the distortions of the voltage signals, a large number of conductors are needed to take measures against the increase of the length of each of the flexible flat cables. As a result, with the increase of the number of the conductors, for example, the flexible flat cables become hard to bend, and this may interfere with the movement of the carriage.
Further, in the printer disclosed in JP-A-2012-206284, one voltage signal (one voltage waveform signal) is transmitted using one coaxial cable (one transmission cable). Thus, in the case where mutually different voltage signals are supplied to a plurality of piezoelectric elements provided in a liquid ejection head to allow the liquid ejection head to eject mutually different kinds of liquids (for example, mutually different colored liquids), coaxial cables whose number is the same as the number of the mutually different voltage signals are needed. Such coaxial cables, however, have a higher rigidity and are harder to bend, as compared with the flexible flat cables. Thus, in such a printer configured to allow a carriage that reciprocates to include a liquid ejection head, when the number of the coaxial cables is increased, that is, when the number of conductors constituting the coaxial cables is increased, for example, a situation in which the coaxial cables, in which the number of the conductors is increased, interfere with the movement of the carriage may occur.
In addition, such a situation is not limited to printers, but is relatively common to printing apparatuses in which voltage signals generated in a voltage signal generation circuit are transmitted to a liquid ejection head from the voltage signal generation circuit using transmission cables, and then are supplied to piezoelectric elements of the liquid ejection head to allow the liquid ejection head to eject liquids.